Inflammation is a process resulting from the dilation and increased permeability of blood vessels at site of injury or infection. Chemokines and cytokines released at the site increase the expression of cell surface proteins on endothelial cells, allowing circulating leukocytes to stick to the vessel wall and migrate to the site of injury/infection within the tissue. These cell surface proteins, termed “cell adhesion molecules” allow the interaction between the leukocytes and the endothelial cells, and mediate the migration of leukocytes into the tissue. Additionally, cell adhesion molecules are required for many of the cell-to-cell interactions in the inflammatory and immune responses. There are three classes of adhesion molecules: selecting, integrins and immunoglobulin-related proteins which can be expressed on leukocytes and endothelial cells. Several of the adhesion molecules, including E-selectin and ICAM, are induced by cytokines such as IL-1 and TNF, and their expression is mediated by the transcriptional factor, NF-κB.
Sustained or inappropriate expression of adhesion molecules can lead to inflammatory or autoimmune disorders. Exaggerated expression of E-selectin and/or ICAM can result in chronic inflammation and has been associated with several inflammatory or autoimmune disorders. Therefore, inhibitors of cell adhesion molecules may be useful for the treatment of these diseases.
Inflammatory and autoimmune diseases are not well managed by current therapy and developments of better drugs are widely pursued. For example, rheumatoid arthritis is a state of chronic inflammation within the joint characterized by cartilage and bone destruction. Traditional therapies for inflammatory or autoimmune disease, such as rheumatoid arthritis, include nonsteroidal anti-inflammatory drugs and salicylates, gold compounds, hydroxychloroquine, sulfasalazine, corticosteroids, oral penicillamines, and cytotoxic or immunosuppressive drugs. However, many of these therapies are not always sufficiently effective and have resulted in serious side effects. More recently, injectable forms of TNFα neutralizing proteins have been successfully marketed for the treatment of rheumatoid arthritis and Crohn's Disease; however, an orally available inhibitor has not been developed for these inflammatory or autoimmune diseases.
Clearly, there remains a need to identify new classes of therapeutic agents for the treatment of inflammatory or autoimmune and proliferative diseases, preferably that are orally available, and are free of serious side effects. It would also be desirable to define new classes of therapeutic agents for the treatment of inflammatory or autoimmune and proliferative disorders in general.